Positive tests for West Nile virus in two horses near Cache Creek serve as a fresh reminder that humans could also be infected by the mosquito-borne disease, health officials say.

"It's not too surprising," said deputy provincial health officer Bonnie Henry. "But it would be the first indication we have this year of any West Nile virus activity."

She noted the two horses haven't yet been confirmed as West Nile cases by the province. They were reported Monday by the Society of B.C. Veterinarians, which cautioned owners of horses against scrimping on their vaccinations.

There have been three bitten-in-B.C. West Nile infections among people over the years, in addition to the more than 40 other cases contracted out of province.

All the local infections happened in 2009 in the Southern Interior, Henry said, with most of the positive tests of mosquitoes and birds occurring in the South Okanagan.

Henry said horses act as "end hosts" like humans – they don't act as a virus reservoir like corvid birds.

"This is another indicator that West Nile virus can be out there," she said. "This would be the highest risk time of year."

Most people bitten by an infected mosquito have no symptoms but in about 20 per cent of cases, those infected develop a fever, headaches and rash. About one in 150 will experience severe complications such as meningitis and about one in 1,000 will die.

The best way to avoid West Nile virus is to prevent mosquito bites: wear light-coloured long-sleeved shirts and pants, especially in the early morning and evening; use repellants with DEET and lemon eucalyptus oil; and eliminate standing water in your yard.

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